If there’s one thing guaranteed to unite a bunch of fractious siblings, it’s a common enemy. You can see it in warring sisters who will round together in anyone who dares join in. You can see it in brothers closing ranks and suppressing all sign of dissent to the outside world in glowering unity.

If you want to extend the concept of siblings further, look at how members of an institution like teachers, firemen, armed forces, churches, or police present a cliff-face of passive resistance to external influences.

It’s tribalism in a small focused group, and the principle scales remarkably well. There’s nothing wrong with it, it’s part of the social glue if you like, that enabled humanity to build it’s civilisation in the first place. An external threat, like refugees, immigrants, virulent illnesses, supply teachers, aliens that hatch from eggs and gestate inside living human hosts, or that new kid who keeps trying to get into the secret treehouse, all provoke visceral defensive reactions and a desire to club together to deny them a foothold.

So that’s why the Mulvaney brothers, or as the long-suffering parents in Riverhampton called them: “The Usual Suspects”, were so determined to beat their new childminder when she unveiled a game of Monopoly. Without even needing to say anything they all came to the simultaneous decision that they could fight it out later, as long as Karla Gabbis was first to be eliminated from the board. She would be forced to retire: broken and bankrupt, any properties to be picked over later as spoils.

In fairly short order, they achieved their goal, and crowed as Karla graciously retreated to let them carry on while she did the washing up. Then she sat down with a big bar of chocolate, a glass of red wine, and Netflix to enjoy the quiet.